Generation and analysis of an electroencephalogram (EEG) is a widely accepted noninvasive procedure for diagnosing a person's neurological system. For example, an EEG can reflect changes in a brain's cellular function due to insufficient oxygen or drugs, to name a few. An EEG system consists of a bio-potential sensor and corresponding monitor to process, analyze and display an EEG signal and corresponding neurological parameters. A bio-potential sensor responds to the electrical potential difference between at least two well-spaced electrodes, using a separate ground electrode. The biopotential monitor typically displays the EEG waveform and a numerical index that reflects changes in the EEG bandwidth and power.
Generation and analysis of a photoplethysmograph is a widely accepted noninvasive procedure for diagnosing a person's cardiovascular system. For example, a photoplethysmograph can yield the oxygen saturation level of arterial blood, an indicator of a person's oxygen supply. A pulse oximetry system consists of an optical sensor applied to a fleshy tissue site, such as a fingertip, and a corresponding pulse oximetry monitor (pulse oximeter). Using multiple wavelength light emitting diodes and a corresponding detector, the optical sensor measures the light absorption of the pulsatile blood at the tissue site. In particular, the optical sensor is responsive to the instantaneous blood volume as well as the blood constituency. Accordingly, the pulse oximeter typically displays a numerical readout of a person's oxygen saturation and pulse rate along with an audible indication of the person's pulse. The photoplethysmograph waveform may also be displayed.
Conventional pulse oximetry assumes that arterial blood is the only pulsatile blood flow in the measurement site. During patient motion, venous blood also moves, which causes errors in conventional pulse oximetry. Advanced pulse oximetry processes the venous blood signal so as to report true arterial oxygen saturation and pulse rate under conditions of patient movement. Advanced pulse oximetry also functions under conditions of low perfusion (small signal amplitude), intense ambient light (artificial or sunlight) and electrosurgical instrument interference, which are scenarios where conventional pulse oximetry tends to fail.
Advanced pulse oximetry is described in at least U.S. Pat. Nos. 6,770,028; 6,658,276; 6,157,850; 6,002,952; 5,769,785 and 5,758,644, which are assigned to Masimo Corporation (“Masimo”) of Irvine, Calif. and are incorporated by reference herein. Corresponding low noise optical sensors are disclosed in at least U.S. Pat. Nos. 6,985,764; 6,813,511; 6,792,300; 6,256,523; 6,088,607; 5,782,757 and 5,638,818, which are also assigned to Masimo and are also incorporated by reference herein. Advanced pulse oximetry systems including Masimo SET® low noise optical sensors and read through motion pulse oximetry monitors for measuring SpO2, pulse rate (PR) and perfusion index (PI) are available from Masimo. Optical sensors include any of Masimo LNOP®, LNCS®, SofTouch™ and Blue™ adhesive or reusable sensors. Pulse oximetry monitors include any of Masimo Rad-8®, Rad-5®, Rad®-5v or SatShare® monitors.
Advanced blood parameter measurement systems are described in at least U.S. Pat. No. 7,647,083, filed Mar. 1, 2006, titled Multiple Wavelength Sensor Equalization; U.S. Pat. No. 7,729,733, filed Mar. 1, 2006, titled Configurable Physiological Measurement System; U.S. Pat. Pub. No. 2006/0211925, filed Mar. 1, 2006, titled Physiological Parameter Confidence Measure and U.S. Pat. Pub. No. 2006/0238358, filed Mar. 1, 2006, titled Noninvasive Multi-Parameter Patient Monitor, all assigned to Masimo Laboratories, Irvine, Calif. (Masimo Labs) and all incorporated by reference herein. Advanced blood parameter measurement systems include Masimo Rainbow® SET, which provides measurements in addition to SpO2, such as total hemoglobin (SpHb™), oxygen content (SpOC™) methemoglobin (SpMet®), carboxyhemoglobin (SpCO®) and PVI®. Advanced blood parameter sensors include Masimo Rainbow® adhesive, ReSposable™ and reusable sensors. Advanced blood parameter monitors include Masimo Radical-7™, Rad87™ and Rad57™ monitors, all available from Masimo. Such advanced pulse oximeters, low noise sensors and advanced blood parameter systems have gained rapid acceptance in a wide variety of medical applications, including surgical wards, intensive care and neonatal units, general wards, home care, physical training, and virtually all types of monitoring scenarios.